This project addresses the clinical applications of functional magnetic resonance imaging (fMRI) to neurosurgical planning, particularly for brain tumors and epileptic foci. If aggressive surgical resection of a tumor or other structural lesion located in or near functionally eloquent cortex is considered, then localization of functional areas relative to the surgical target must be ascertained in order to avoid a postoperative neurological deficit. This is particularly critical for aggressive resection of brain tumors because normal cortical landmarks are distorted by the tumor mass. The need to avoid functionally critical areas is particularly critical in patients whose only symptom is epilepsy. Such patients tend to have benign or indolent non-life-threatening lesions, and a postoperative neurological deficit may represent an unacceptable surgical risk. Traditional methods of neurosurgical functional cortical brain mapping require surgical exposure of the brain surface before any functional information is obtained. FMRI, on the other hand, is non-invasive, can be performed on an out-patient basis, and is performed before any commitment to perform a neurosurgical procedure has been made. Despite these potential advantages implementation of fMRI in surgical planning has been impeded in large measure by motion artifacts. The effect of inter-image head motion on an fMRI time series is twofold: 1) to mask the detection of pixels which undergo true positive physiological activation, and 2) to create areas of spurious or false positive activation which are due to stimulus correlated head motion. Aim #1 of this proposal is concerned with the development and testing of real-time correction of image to image bulk head motion during fMRI. Aim #2 will test the hypothesis that real-time correction techniques improve the fidelity of fMRI sensorimotor mapping in volunteer subjects. Aim #3 will test the same hypothesis in neurosurgical patients who later undergo surgical functional brain mapping. The applicants believe that prospective correction using navigator and orbital navigator echoes is the most rational solution to the problem of head motion in fMRI both when applied to surgical planning and in other studies of brain function.